Systems and methods for delivering radiotherapy

ABSTRACT

A radiotherapy system and method for delivering radiotherapy are provided. In some aspects, the radiotherapy system includes beam director comprising a radiation source configured to generate radiation for irradiating a patient, the beam director having at least four degrees of freedom of movement. The radiotherapy system also includes a controller configured to operate the beam director to irradiate the patient in accordance with a radiation treatment plan, wherein the radiation treatment plan is generated based on a solution space determined by the at least four degrees of freedom of movement of the beam director.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with government support under R44CA183390, andR43CA183390 awarded by the National Institutes of Health. The governmenthas certain rights in this invention.

BACKGROUND

The present disclosure relates, in general, to external beam radiationtherapy systems and methods, and more particularly to external beamradiation therapy systems and methods having a beam director with atleast four degrees of freedom.

Conventional external beam radiation therapy, also referred to as“teletherapy,” is commonly administered by directing beams of ionizingradiation produced by a linear accelerator (“LINAC”) toward a definedtarget volume in a patient. Radiation dose with a specific profile canbe built up in the target by shaping the beams into treatment fieldsusing collimators and other devices, and irradiating the patient forcertain amounts of time using the shaped beams. In preparing a radiationtreatment plan, planning images, such as computed tomography (“CT”), areused to select beam configuration that optimize therapeutic effects andreduce radiation-induced side effects.

In addition, medical imaging can also be used concurrently with thedelivery of radiation therapy in a technique called image-guidedradiation therapy (“IGRT”). Using positional information from the imagesto supplement the radiation treatment plan, IGRT can improve theaccuracy of the delivered radiation. This allows for radiation doseimparted to targeted regions to be escalated to achieve better outcomes,with reduced risk to healthy tissues.

Intensity modulated radiation therapy (“IMRT”) is an external beamradiation therapy technique that utilizes computer planning software toproduce a three-dimensional radiation dose map specific to locations,shapes and motion characteristics target and non-target structures in apatient. To do so, IMRT utilizes multiple beams that may beindependently controlled in intensity and energy. Specifically, eachbeam includes a number of sub-beams or beamlets whose individualintensity can be varied to modulate the beam. Using this technique,specific regions within a targeted tumor, as well as other target andnon-target structures in the patient's anatomy, can receive differentradiation dose intensities.

The quality of radiation therapy delivered to a patient depends at leastin part upon the spatial arrangement and intensity modulation of beams.When beam orientations are optimized, the quality of therapy can besignificantly improved. However, optimized plans often requirenon-coplanar beams, which can be difficult to deliver using conventionalLINACs. This is because these machines utilize gantries that have onlyone degree of rotational freedom. To address this, treatment plans ofteninclude patient couch repositioning. However, coordinating gantry andcouch motion, along with imaging, can complicate treatment and introducethe potential for significant problems. For example, collisions, patientmovement and difficulties with monitoring of the patient using imaging,can interfere with treatment and lead to possible equipment damage andpatient injury. In addition, mechanical constraints on couch and gantrymovements only provide a limited number of additional beam orientations.In many cases, such limited beam configurations can prevent cliniciansfrom reaching the optimal plan quality and therefore the best treatmentoption.

Therefore, there is a need for improved systems and methods fordelivering radiotherapy treatment.

SUMMARY

A radiotherapy system and method for delivering radiotherapy areprovided. Features and advantages of the present disclosures may beappreciated from descriptions below.

In one aspect of the present disclosure, a radiotherapy system isprovided. The radiotherapy system includes beam director comprising aradiation source configured to generate radiation for irradiating apatient, the beam director having at least four degrees of freedom ofmovement. The radiotherapy system also includes a controller configuredto operate the beam director to irradiate the patient in accordance witha radiation treatment plan, wherein the radiation treatment plan isgenerated based on a solution space determined by the at least fourdegrees of freedom of movement of the beam director.

In another aspect of the present disclosure, a method for delivering aradiation treatment plan to a patient using a radiotherapy system isprovided. The method includes generating, based on a dose prescription,a radiation treatment plan optimized from a solution space determined bya beam director of a radiotherapy system having at least four degrees offreedom of movement. The method also includes receiving imaginginformation acquired from a patient. The method further includescontrolling the radiotherapy system to deliver the radiation treatmentplan based on the imaging information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a radiotherapy system, in accordancewith aspects of the present disclosure.

FIG. 1B is a schematic diagram of an example a beam director for theradiotherapy system of FIG. 1A.

FIG. 1C is an illustration comparing the solution space for aconventional C-arm radiotherapy system and the solution space for aradiotherapy system, in accordance with aspects of the presentdisclosure.

FIG. 2A is an image showing one example of the radiotherapy system ofFIG. 1A.

FIG. 2B is an illustration showing one example of an articulated arm, inaccordance with aspects of the present disclosure.

FIG. 3 is a flowchart setting forth steps of a process, in accordancewith aspects of the present disclosure.

FIG. 4A are images comparing dose distributions, optimized forconventional radiotherapy systems and a radiotherapy system according tothe present disclosure, for an example treatment head and neck case.

FIG. 4B are images comparing dose distributions, optimized forconventional radiotherapy systems and a radiotherapy system according tothe present disclosure, for an example lung case.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure is directed to systems and methods for radiationtherapy that can overcome one or more of the above-described drawbacks.Among other advantages, the present disclosure describes a novelapproach for delivering radiotherapy that provides superior dosimetryand reduces treatment times as compared to conventional treatmentmethods.

Referring particularly to FIG. 1A, the schematic diagram of aradiotherapy system 100, in accordance with aspects of the presentdisclosure, is shown. As shown, the radiotherapy system 100 maygenerally include a delivery system 102, an imaging system 104, andoptionally a positioning system 106, each in communication with atreatment console 108. The delivery system 102 is configured to generateand direct radiation to a patient positioned on a treatment table 110,in accordance with a radiation treatment plan, where the treatment table110 may be fixed or movable. The imaging system 104 may be configured toimage the patient before, during or after treatment. Although shown inFIG. 1A as a separate system, in some embodiments, the imaging system104 may be part of, or combined with, the delivery system 102. Thepositioning system 106 may be configured to position and orient thetreatment table 110. In addition, the positioning system 106 may also beconfigured to move the patient to the imaging system 104.

The treatment console 108, or another suitable controller, may beconfigured to receive a radiation treatment plan from a planningworkstation 112, or another location, such as a database 114, server 116or cloud 118. Thereafter, the treatment console 108 may control thedelivery system 102, imaging system 104 and optionally positioningsystem 106 to execute the radiation treatment plan. During treatment,the delivery system 102 builds radiation dose inside a patient toachieve dose distributions in accordance with the radiation treatmentplan. The plan may include a number of treatment fields having variousbeam numbers, beam shapes or fluences, beam energies, beam orientationsrelative to the patient, and durations of exposure. In delivering theradiation treatment plan, the table 110 and patient may advantageouslykept stationary, while the delivery system 102 is moved about thepatient. This provides the ability to using beam angles that cover asignificant portion of the 4 π solid angle about the patient, includingbeam directions or beam orientations posterior in relation to thepatient. In addition, errors associated with physically moving the table110 and patient may also be avoided. Optionally, the radiation treatmentplan may also be executed using a combination of table 110 and deliverysystem 102 movements.

In one embodiment, the delivery system 102 may include a beam director150 that is configured to irradiate a patient from a plurality ofdirections, as shown schematically in FIG. 1B. The beam director 150 mayinclude a base 152 providing support for the beam director 150, and anarticulated arm 154 mechanically linked to the base 152. The beamdirector 150 may also include a treatment head 156 that is mechanicallylinked to the articulated arm 154. In some implementations, the beamdirector 150 may form, or be part of, a robotic system that may becontrolled by the delivery system 102 or treatment console 108 of FIG.1A.

Specifically, the treatment head 156 may be configured to house aradiation source 158, such as a linear accelerator (“LINAC”), as well asvarious elements and hardware for controlling radiation produced by theradiation source 158. For example, the treatment head 156 may includeone or more collimators 160 (e.g., a multileaf collimator), and otherelements, such as filters (e.g. flattening filters), foils (e.g.scattering foils), and waveguides. The radiation source 158 may beconfigured to generate radiation (e.g. X rays, electrons, and so on)having energies sufficient to produce desired therapeutic orradiobiological effects, such as the destruction of malignant tissue.More specifically, the energies of the radiation produced by theradiation source 158 are less than 6 MeV, although other energies mayalso be possible.

Although the radiation source 158 and collimator 160 are shown in FIG.1B to be physically separated, in some implementations, the radiationsource 158 and collimator 160 may be positioned directly adjacent to oneanother, or within a sufficiently close distance (e.g. less than 10 mm).In particular, the collimator 160 may be positioned adjacent to anoutput of the radiation source 158. In addition, the treatment head 156,and elements therein may be constructed with a reduced size anddimensions (as compared to conventional radiation treatment systems).This is advantageous for reducing the overall footprint of the deliverysystem 102. Also, a reduced size provides access to a patient fromposterior angles, which are not accessible by existing robotic systems.

During the planning stage, a radiation treatment plan is often optimizedto provide a conformal radiation dose to target tissues, in accordancewith dosing prescriptions, while avoiding critical structures in apatient and reducing treatment time. As described, optimized treatmentplanning may often require the ability to provide coplanar andnon-coplanar beam configurations relative to the patient. In addition,treatment field characteristics included in the radiation treatmentplan, such as beam orientation and fluence, are determined by themovement capability of particular system utilized. Therefore, in someaspects, a radiation treatment plan delivered using the radiotherapysystem 100 may be optimized from a very large solution space.

Therefore, at least a portion of the beam director 150 (e.g. thetreatment head 156) may have freedom of movement of at least four and upto six degrees of freedom. For instance, the articulated arm 154 mayinclude at least two joints providing the beam director 150 flexibilityof movement spanning a significant portion of a 4 π solid angle aboutthe patient (e.g. greater than about 60% of the 4 π solid angle). Theability to cover a large portion of the solid angle represents asignificant improvement over previous C-arm gantry radiotherapy systems,which typically can access around 15%-60% of the solid angle. Inaddition, the movement capability of the beam director 150 allows forvaried source-to-tumor distances, or source-to-axis distances (“SADs”),during treatment. To provide the full ability to direct or orient beamsaround a patient as necessary, in some implementations, the beamdirector 150 may be configured to move the treatment head 156 alongthree spatial axes (e.g. x, y and z axes), to orient the treatment head156 using three rotational axes (e.g. yaw, pitch and roll), or achievemovement using a combination thereof.

To visually illustrate this point, FIG. 1C shows a comparison betweenthe solution space for a conventional C-arm gantry radiotherapy system(left side), and a solution space for a radiotherapy system of thepresent disclosure (right side). As appreciated from the figure, havingmovement capability with at least four degrees of freedom allowscoverage of the full solid angle access about the patient. By contrast,the C-arm radiotherapy system is substantially limited.

The ability to cover a significant portion of the 4 π solid angle canreduce the need for deep penetration of radiation into a patient.Accordingly, the beam director 150 of FIG. 1B need not require ahigh-energy radiation source. Rather, the radiation source 158 mayinclude low-energy source or accelerator configured to providelow-energy radiation (i.e. less than conventional 6 MeV). In fact, andunexpectedly, results show that lower energy radiation can providesuperior performance. This may be due, in part, to the decreased size ofthe lateral penumbra, and increased dose compactness produced by thebeam director 150. In addition, lower energy radiation reduces the sizeand weight requirements of the radiation source 158, and simplifies thedesign of the collimator 160. Furthermore, lower energies also reduceshielding requirements for the treatment head 156 and treatment room.

Referring again to FIG. 1A, the planning workstation 112 may be utilizedto generate a radiation treatment plan based on dosimetric prescriptionsand imaging information obtained from a subject. As described,generating the plan include selecting appropriate treatment fields,which can vary in number, duration, shape or fluence, energy andorientation relative to the patient, to optimize patient outcomes. Insome applications, variable SADs may be needed to avoid an undesiredcompromise between field size and intensity modulation resolution.Furthermore, variable SADs allow for both larger and smaller tumors tobe treated optimally. However, combining a large number of optionsafforded by the significant portion of a 4 π solid angle, with variousradiation field parameters (e.g. duration, shape, energy, direction,fluence, SADs, and others) necessitates an optimization algorithmcapable of taking into account a large solution space. To this end, theplanning workstation 112 may be configured to perform an integrated beamorientation and optimization method to generate the radiation treatmentplan. In some aspects, treatment field characteristics, such as beamorientation, may be optimized for both dosimetry and efficiency. As anexample, an optimization approach developed by the inventors anddescribed in PCT/US2016/020234, which is incorporated herein byreference, in its entirety, may be used, although other approaches mayalso be possible.

In some implementations, the planning workstation 112 may include one ormore processors configured to execute non-transitory software orprogramming that includes steps for carrying out an optimizationalgorithm in a solution space determined by a radiotherapy system, andmore specifically a beam director, having at least four degrees offreedom of movement. As described, such solution space may cover 60% ormore of the 4 π solid angle about the patient. More specifically, thesolution space covers at least 90% of the 4 π solid angle. In someimplementations, at least one processor in the planning workstation 112may include hardwired instructions or programming for carrying out anoptimization algorithm, as described. Such processor would therefore bea special-purpose processor, by way of its specialized programming.

By way of non-limiting example, FIG. 2A-B illustrate one embodiment of aradiotherapy system 200, in accordance with aspects of the presentdisclosure. The radiotherapy system 200 includes a beam director 202 andpatient table 204. As shown, the patient table 204 is fixed. The beamdirector 202 includes a base 206, an articulated arm 208 and a treatmenthead 210. As described, the treatment head 210 may include a radiationsource (i.e. a LINAC), a collimator (i.e. a multi-leaf collimator), andother elements and circuitry. The motion of beam director 202 can becontrolled by a beam director controller, which can communicate with oneor more operator workstations or computers. As appreciated from FIGS. 2Aand 2B, the radiotherapy system 200 allows beam directions that span upto a full solid angle about the patient.

Referring specifically to FIG. 2B, the articulated arm 208 may include anumber of pivoting points or joints allowing up to six degrees offreedom of movement of the beam director 202, and radiation source,about the patient. As shown, a first joint 212, a second joint 214, athird joint 216, a fourth joint 218, a fifth joint 220, and a sixthjoint 222 allow rotation of the articulated arm 208 about a first axisA1, a second axis A2, a third axis A3, a fourth axis A4, a fifth axisA5, and a sixth axis A6, respectively.

Turning now to FIG. 3, a flowchart setting forth steps of a process 300in accordance with aspects of the present disclosure is shown. Theprocess 300, or various steps therein, may be carried on or using anysuitable device, apparatus or system, such as the radiotherapy systemdescribed with reference to FIG. 1A. In some implementations, the stepsof the process 300 may be performed by one or more processors orcomputers configured to execute programming or instructions stored innon-transitory computer readable media. The processor(s) may be includegeneral-purpose processors, as well as application-specific processorshaving programming or executable instructions hardwired therein.

The process 300 may begin at process block 302 with generating aradiation treatment plan. As described, the radiation treatment plan maybe optimized from a solution space that is determined by the deliverysystem of a radiotherapy system, and more particularly, a beam directorhaving at least four degrees of freedom of movement. As such, anoptimization algorithm may be executed at process block 302 to generatethe radiation treatment plan. In particular, the optimization algorithmmay be configured to select beam configurations achieving dosimetricprescriptions based on the solution space determined by the beamdirector. In some aspects, the optimization algorithm may optimize adosimetry and an efficiency of delivery beams in the radiation treatmentplan.

In one non-limiting example, the solution space covers at least 60% ofthe 4 π solid angle about the patient, and more specifically at least90% of the 4 π solid angle. In generating the radiation treatment plan,the various movements performed or paths navigated by the beam directormay also be determined. Such movements and paths may be optimized tominimize patient treatment time and treatment efficiency, as well as toavoid collisions with the patient, the patient table and other equipmentpresent during treatment.

Then at process block 304, imaging information acquired from a patientprior to treatment may be received. Such imaging information may be inthe form of radiographs, CT's, MRI, video and other imaging information.In some aspects, the radiation treatment plan may be adapted based onanalysis of the imaging information received at process block 302. Forexample, a position, alignment or orientation of the patient may bedetermined based on the imaging information and used to adapt or correctthe radiation treatment plan. In some aspects, correction of patientposition, alignment or orientation may be performed without physicallymoving the patient or patient table.

Then at process block 304, the radiation treatment plan is delivered bycontrolling the radiotherapy system based on the imaging information. Insome aspects, the radiation treatment plan may be delivered using adelivery system that is configured to selectively access a 4 π solidangle about the patient.

A report, in any form, may then be optionally generated, as indicated byprocess block 308. For example, the report may indicate a status orcompletion of treatment field(s), a treatment progress, treatmentinterruptions or errors, positioning of the delivery system andcomponents therein, and so on.

FIGS. 4A and 4B illustrates a comparison of dose distributions forexample head and neck and lung cases. The dose distributions wereoptimized for a conventional radiotherapy system, as indicated by label400, and for a radiotherapy system, in accordance with aspects of thepresent disclosure, as indicated by label 402. As appreciated from thefigures, the present approach provides more conformal distributionscompared to the previous technique, which would results in reducedradiation exposure to non-targeted tissues.

The system and method for delivering radiotherapy described hereinprovide a number of advantages over existing radiotherapy systems.First, the dosimetry achievable herein is superior to methods that arelimited to coplanar beam configurations. For example, a 20-40% normalorgan dose reduction can be achieved using the approach describedherein. Second, compared to coplanar plans generated for radiotherapysystems having C-arm gantries, treatment time can be reduced from 50minutes to less than 15 minutes using the present approach. Third,patient secondary movements, due to table motion, can be minimized bykeeping the patient static during the entire treatment. Third,optimizing the beam orientation and fluence maps together results insignificantly superior dosimetry as shown in FIGS. 4A-4B. Fourth, thereduced size of the treatment head of a beam director (i.e., the LINACtreatment head) allows full access to the posterior beam angles that canoften be critical to plan quality. Finally, utilizing an optimizationalgorithm that can address both small and large tumors providesincreased flexibility for the radiotherapy system described here, whichcan increase the number of patients that can be treated in a day (e.g.,3-4 times more patients) as compared to conventional radiotherapysystems.

Features suitable for such combinations and sub-combinations would bereadily apparent to persons skilled in the art upon review of thepresent application as a whole. The subject matter described herein andin the recited claims intends to cover and embrace all suitable changesin technology.

1-16. (canceled)
 17. A radiotherapy system comprising: a radiationsource configured to generate radiation for irradiating a patient; and acontroller configured to operate the radiotherapy system to irradiatethe patient in accordance with a radiation treatment plan, the radiationtreatment plan being generated based on a solution space that covers atleast 60% of a 4 π solid angle about a patient.
 18. The radiotherapysystem of claim 17, wherein the radiation treatment plan comprises abeam orientation that is posteriorly angled relative to the patient, andwherein the radiation source is configured to emit radiation along thebeam orientation towards the patient at a proximal end of the beamorientation, and wherein the proximal end of the beam orientation ispositioned below a table that supports the patient.
 19. The radiotherapysystem of claim 18, further comprising a treatment head that includesthe radiation source is configured to be positioned below a table thatsupports the patient to deliver radiation along the beam orientationthat is posteriorly angled.
 20. The radiotherapy system of claim 19,further comprising the table that supports the patient, the table beingconfigured to be stationary while a delivery system that includes theradiation source is moved about the patient.
 21. The radiotherapy systemof claim 17, further comprising an articulated arm and a treatment headcoupled to the articulated arm, the articulated arm having a firstjoint, and a second joint.
 22. The radiotherapy system of claim 21,wherein the treatment head has at least four degrees of freedom ofmovement, and wherein the solution space has been determined by the atleast four degrees of freedom of movement of the treatment head.
 23. Theradiotherapy system of claim 17, wherein the solution space covers atleast 90% of the 4 π solid angle about the patient.
 24. The radiotherapysystem of claim 17, wherein the radiation treatment plan is optimizedfrom the solution space that covers at least 60% of the 4 π solid angleabout the patient.
 25. The radiotherapy system of claim 17, furthercomprising a beam director that includes a treatment head having theradiation source, and wherein the beam director is configured to movethe treatment head along three spatial axes.
 26. The radiotherapy systemof claim 17, wherein the radiation treatment plan has been generatedusing a variable source-to-axis distance (“SAD”).
 27. A radiotherapysystem comprising: a radiation source configured to generate radiationfor irradiating a patient; and a controller configured to operate theradiotherapy system to irradiate the patient in accordance with aradiation treatment plan, the radiation treatment plan comprising a beamorientation that is posteriorly angled relative to the patient, theradiation source is configured to emit radiation along the beamorientation towards the patient at a proximal end of the beamorientation, and the proximal end of the beam orientation is positionedbelow a table that supports the patient.
 28. The radiotherapy system ofclaim 27, wherein the radiation treatment plan is generated based on asolution space that covers at least 60% of a 4 π solid angle about apatient.
 29. The radiotherapy system of claim 28, wherein the solutionspace covers at least 90% of the 4 π solid angle about the patient. 30.A method comprising: determining a solution space that covers at least60% of a 4 π solid angle about a patient; and generating a radiationtreatment plan based on the solution space.
 31. The method of claim 30,wherein determining the solution space is based on a beam director of aradiotherapy system having at least four degrees of freedom of movement,and
 32. The method of claim 30, wherein generating the radiationtreatment plan based on the solution space includes optimizing thesolution space to generate the radiation treatment plan, the radiationtreatment plan including a plurality of different beam orientationsrelative to the patient.
 33. The method of claim 32, wherein a firstbeam orientation of the plurality of different beam orientations isposteriorly angled relative to the patient, and wherein a proximal endof the beam orientation in which a radiation source emits radiationtowards the patient at is positioned below a table that supports thepatient.
 34. The method of claim 30, further comprising: receivingimaging information acquired from a patient; analyzing the imaginginformation; and adapting the radiation treatment plan, based on theanalyzing of the imaging information.
 35. The method of claim 34,wherein adapting the radiation treatment plan includes: determining aposition, an alignment, or an orientation of the patient based on theimaging information; and correcting the radiation treatment plan basedon the position, the alignment, or the orientation of the patient,without physically moving the patient.
 36. The method of claim 34,wherein the imaging information is at least one of a radiograph, acomputed tomography (CT) scan, or a magnetic resonance imaging (MRI)scan.